Automatic automobile transmission with variable shift pattern controlled in response to estimated running load

ABSTRACT

An automatic transmission control system for an automobile, comprising a vehicle weight estimation unit which estimates a vehicle weight of the automobile a torque estimation unit which estimates an output torque, an acceleration input unit which accepts an acceleration signal; a load estimation unit (110) which estimates a running load from the estimated vehicle weight, the estimated output torque and the accepted acceleration; a memory which stores a plurality of shift schedules therein; and a gear position determination unit (109) which includes the memory, and which selects one of the shift schedules in accordance with the vehicle weight and the estimated running load, so as to determine a gear position of an automatic transmission of the automobile in conformity with the selected shift schedule. An exact shift operation conformed to the vehicle weight and the running load can be performed, and an enhanced fuel consumption can be attained.

This application is a continuation of reissue application Serial No.09/064,765, filed Apr. 23, 1998, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to transmission control systems forautomobiles.

A prior-art transmission control system for an automobile is soconstructed that a vehicle speed and a throttle valve opening are sensedas electric signals, and that a predetermined shift gear correspondingto the current values of the vehicle speed and the throttle valveopening is selected on the basis of a shift pattern which is preset,with the vehicle speed and the throttle valve opening as variables.Herein, a plurality of such shift patterns are set beforehand, and oneof them is selected by the manipulation of the driver of the automobile.

In another transmission control system, the shift patterns areautomatically selected and changed-over in accordance with the drivingoperation of the driver.

The control of a transmission in the prior art is such that apredetermined gear position corresponding to the current values of avehicle speed and a throttle valve opening is selected on the basis of ashift pattern which is preset, with the vehicle speed and the throttlevalve opening as variables.

In addition, the official gazette of Japanese Patent ApplicationPublication No. 45976/1988 discloses a technique wherein a torque isevaluated from the pressure of an intake pipe, and a transmission gearratio [(r.p.m. of an internal combustion engine)/(vehicle speed)] isdetermined from the torque.

These methods have made performing an exact shift operation for thefluctuations of drive conditions difficult, especially for the change ofa running load. For example, it is considered that the fuel consumptionof the automobile will be enhanced without spoiling the drivabilitythereof, by upshifting earlier on a flat road or a gentle downward sloperather than on an upward slope. Such a shift operation, however, hasheretofore been impossible because of the gear shift based on only thethrottle valve opening and the vehicle speed.

Besides, as the vehicle is lightened, it becomes important to performthe shift control so as to correspond to the change of accelerationcharacteristics dependent upon the weight of the vehicle in the case ofa starting acceleration. It is therefore considered possible to enhancethe fuel consumption and to perform the exact shift operationcorresponding to the drive conditions, in such a way that the runningload and the vehicle weight are estimated, and that the shift pattern ischanged in accordance with the vehicle weight and the running load in anaccelerating mode, while it also is changed in accordance with therunning load in a decelerating mode.

Since the shift pattern is determined on the basis of the severaltypical drive conditions as stated above, the prior-art techniques havebeen sometimes incapable of the shift operation which reflects the driveconditions exactly. As a result, they have often worsened the fuelconsumption.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an automatictransmission control system for an automobile in which the running loadof the automobile is estimated so as to perform a shift operation whichconforms to the running load.

In order to accomplish the object, an automatic transmission controlsystem for an automobile in one aspect of performance of the presentinvention is constructed comprising load computation means for computingthe automobile load; output torque estimation means for calculating anoutput torque with reference to the torque characteristics of the drivetrain of the automobile; running load estimation means for estimating arunning load from the automobile load and the output torque; memorymeans for storing at least two shift schedules therein; and a shiftschedule variable-control unit which determines a shift schedule of anautomatic transmission of the automobile during actual running of theautomobile, on the basis of the estimated running load and the storedshift schedules.

Besides, in order to perform a shift operation which is based on, notonly a running load, but also an estimated vehicle weight of anautomobile, an automatic transmission control system for an automobilein another aspect of performance of the present invention may well beconstructed comprising vehicle weight estimation means for estimatingweight of the automobile; torque estimation means for estimating anoutput torque; acceleration input means for accepting an accelerationsignal; running load estimation means for estimating the running loadfrom the estimated vehicle weight, the estimated output torque and theinput acceleration; memory means for storing a plurality of shiftschedules therein; and gear position determination means for selectingone of the shift schedules on the basis of the vehicle weight and theestimated running load, and for determining a gear position of anautomatic transmission of the automobile in accordance with the selectedshift schedule.

In operation, the running load (and the vehicle weight) are estimated,and the shift operation is performed in conformity with the vehicleweight and the running load. Therefore, the optimal shift pattern isformed in accordance with a driving environment such as a mountain path,to enhance the drivability of the automobile. Moreover, on a flat road,the fuel consumption of the automobile is enhanced.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a shift control system which includes anautomatic transmission control system in an embodiment of the presentinvention;

FIG. 2 is a schematic block diagram showing the hardware elements of theshift control system depicted in FIG. 1;

FIG. 3 is an explanatory diagram showing the details of input signals toand output signals from an AT (automatic transmission) control unit;

FIG. 4 is a block diagram of a vehicle weight estimation section whichincludes vehicle weight estimation means;

FIG. 5 is a diagram for explaining the time serialization of anacceleration response waveform;

FIGS. 6A and 6B are diagrams for explaining a method of starting thetime serialization;

FIG. 7 is a diagram for explaining the flow of processing for thegeneration of a time serialization start signal;

FIG. 8 is a flow chart showing the processing steps of means forgenerating the time serialization start signal;

FIG. 9 is a diagram for explaining the learning method of a neuralnetwork which is used in the vehicle weight estimation means depicted inFIG. 4;

FIG. 10 is a block diagram of a shift control section which includestorque converter-generated torque estimation means, engine-generatedtorque estimation means and load estimation means;

FIGS. 11(a) and 11(b) are graphs showing an engine torque map and atorque converter characteristic map, respectively;

FIG. 12 is a flow chart showing a process for estimating an accessorytorque;

FIG. 13 is a flow chart showing a process for estimating a torquegenerated by an engine;

FIG. 14 is a flow chart showing a process for estimating an outputtorque based on a torque converter;

FIG. 15 is a flow chart showing a process for estimating a running loadtorque from the estimated output torque;

FIG. 16 is a flow chart showing another method of the process forestimating the accessory torque;

FIG. 17 is a schematic block diagram for explaining gear positiondetermination means;

FIGS. 18(a) and 18(b) are explanatory diagrams showing shift maps in amethod of altering shift schedules which are based on load estimationand vehicle weight estimation;

FIG. 19 is a block diagram of an automatic transmission control systembeing another embodiment in which a shift schedule is continuouslyvaried in consideration of a grade or slope;

FIG. 20 is an explanatory diagram showing a shift map in the embodimentillustrated in FIG. 19; and

FIGS. 21(a), 21(b) and 21(c) are graphs for explaining how to decide anacceleration request.

PREFERRED EMBODIMENTS OF THE INVENTION

Now, embodiments of the present invention will be described withreference to the drawings. In the ensuring description, an expression“change gear ratio” or “gear ratio” shall mean the product between thegear ratio of a transmission and that of a final drive.

The schematic construction of an automatic transmission control systemfor an automobile in one embodiment of the present invention isillustrated in FIG. 1.

Throttle valve opening (TVO) sensing means 101 senses a throttle valveopening 121 in the automobile, which is delivered to vehicle weightestimation means 106, engine-generated torque estimation means 1001 andgear position determination means 109.

Acceleration sensing means 102 senses the acceleration 122 of theautomobile, which is delivered to the vehicle weight estimation means106 and load estimation means 110.

Vehicle speed sensing means 103 senses the vehicle speed 123 of theautomobile, which is delivered to the vehicle weight estimation means106 and the gear position determination means 109.

Engine r.p.m. sensing means 104 senses engine r.p. m. (“revolutions perminute” also termed an “engine speed”) 124 in the automobile, which isdelivered to torque converter-generated torque estimation means 107 andthe engine-generated torque estimation means 1001. The torqueconverter-generated torque estimation means 107 and the engine-generatedtorque estimation means 1001 are means for estimating torques generatedby the torque converter of the automobile and the engine thereof,respectively.

Turbine r.p.m. sensing means 105 senses turbine r.p. m. (also termed a“turbine speed”) 125 in the automobile, which is delivered to the torqueconverter-generated torque estimation means 107.

In the vehicle weight estimation means 106, the vehicle weight of theautomobile is estimated on the basis of the throttle valve opening 121,acceleration 122 and vehicle speed 123. The estimated vehicle weight 126is delivered to the gear position determination means 109 and the loadestimation means 110.

In the torque converter-generated torque estimation means 107, thetorque generated by the torque converter is estimated from the enginespeed 124 and the turbine speed 125. The estimated torque 1022 generatedby the torque converter is delivered to the load estimation means 110.

In the engine-generated torque estimation means 1001, the torquegenerated by the engine is estimated from the throttle valve opening 121and the engine speed 124. The estimated torque 1015 generated by theengine is delivered to the torque converter-generated torque estimationmeans 107.

In the load estimation means 110, a load torque is estimated from theestimated vehicle weight 126, the estimated torque 1022 generated by thetorque converter, and the acceleration 122. The estimated load torque1028 is delivered to the gear position determination means 109.

In the gear position determination means (which is also means forstoring shift schedules therein) 109, a gear position is determined onthe basis of the throttle valve opening 121, vehicle speed 123, vehicleweight 126 and load torque 1028. The determined gear position 129 isdelivered to hydraulic drive means 111.

The hydraulic drive means 111 determines the driving hydraulic pressureof the clutch of the automatic transmission and drives the clutch so asto establish the determined gear position 129.

FIG. 2 illustrates the arrangement of an engine and drive train and acontrol unit therefor for use in the embodiment of the presentinvention. An engine 201 and a transmission 202 supply the AT (automatictransmission) control unit 203 with signals 204 and 205 indicative oftheir respective operating states. In addition, vehicle signals 207 andASCD (auto speed cruising device) control unit signals 208 are input tothe AT control unit 203. In the AT control unit 203, a gear position isdetermined from the received signals so as to deliver shift instructionsignals 206 to the transmission 202.

FIG. 3 illustrates the details of the signals shown in FIG. 2. Signals304 thru 307 in FIG. 3 correspond to the engine output signals 204 inFIG. 2, while signals 308 thru 310 correspond to the transmission outputsignals 205. Besides, signals 311 thru 314 correspond to the vehiclesignals 207, while signals 315 and 316 correspond to the ASCD controlunit signals 208. On the other hand, signals 317 thru 321 correspond tothe AT control unit signals 206. In FIG. 3, the input signals 304 ˜ 316are supplied to an AT control unit 301 through an input signalprocessing unit 302. Further, the output signals 317 ˜ 321 from the ATcontrol unit 301 are delivered through an output signal processing unit303.

In the present invention, a vehicle weight estimating method utilizesthe fact that the vehicle acceleration and the vehicle speed, whicharise when the driver of the automobile has depressed the acceleratorpedal thereof, differs depending upon the vehicle weight. Thus, thevehicle weight is recognized from an accelerating response waveform.With this method, the cost of the control system is not increased by theuse of a sensor for measuring the vehicle weight, and the vehicle weightcan be estimated with a precision satisfactory for the shift control ofthe automatic transmission.

FIG. 4 is a detailed block diagram showing an example of the vehicleweight estimation means 106 depicted in FIG. 1. In FIG. 4, accelerationsensing means 401 delivers an acceleration signal 411 to timeserialization means (acceleration input means) 405 and timeserialization start signal generation means 404. Vehicle speed sensingmeans 402 delivers a vehicle speed signal 412 to the time serializationmeans 405. TVO sensing means 403 delivers a throttle valve openingsignal 413 to the time serialization means 405 and the timeserialization start signal generation means 404.

The time serialization start signal generation means 404 monitors boththe signals of the acceleration 411 and the throttle valve opening 413,and it sends a signal 416 to the time serialization means 405 to starttime serialization when the acceleration has risen owing to the driver'sdepression of the accelerator pedal, in other words, in conformity withthe accelerating response waveform.

Upon receiving the time serialization start signal 416, the timeserialization means 405 time-serializes the acceleration 411, vehiclespeed 412 and throttle valve opening 413 so as to deliver time-serialsignals 414 to neural vehicle weight estimation means 406. The neuralvehicle weight estimation means 406 estimates the vehicle weight on thebasis of the received time-serial signals 414, and delivers an estimatedvehicle weight 415.

FIG. 5 is a diagram for explaining the time serialization of theaccelerating responses of the acceleration, vehicle speed and throttlevalve opening. The time serialization is started at the point of timetso at which the acceleration has exceeded a predetermined thresholdvalue αth. Then, the acceleration, vehicle speed and throttle valveopening are sampled at regular intervals of Δt.

The reason why the threshold value is set for the acceleration will beelucidated with reference to FIGS. 6A and 6B. In a case where athreshold value is set for the throttle valve opening for the purpose ofthe time serialization in the accelerating mode and where the samplingis initiated in synchronism with the rise of the throttle valve opening,the rise of the longitudinal acceleration (the acceleration in thelongitudinal direction of the body of the automobile) becomes discrepantbecause of an individual difference involved in the way the driverdepresses the accelerator pedal. In order to eliminate the discrepancy,the threshold value is set for the acceleration, and the sampling isstarted when the acceleration has exceeded the threshold value.

FIG. 7 illustrates the procedure of the processing of the timeserialization start signal generation means 404 shown in FIG. 4. First,the closure of a throttle valve is confirmed. Subsequently, the openingof the throttle valve rises and exceeds the preset threshold value.Thereafter, the time serialization is initiated when the accelerationhas exceeded the threshold value.

FIG. 8 illustrates the flow of that processing of the time serializationstart signal generation means 404 which corresponds to FIG. 5. Morespecifically, whether or not the throttle valve is closed is checked ata step 801. When the throttle valve is closed, the processing flowproceeds to a step 802, and when not, it returns to the step 801.Further, when the throttle valve opening θ has exceeded its thresholdvalue θth at the step 802, the processing flow proceeds to a step 803,and when not, it returns to the step 802. On condition that theacceleration α has exceeded its threshold value αth at the step 803, theprocessing flow proceeds to a step 804. Otherwise, the processing flowreturns to the step 803. At the step 804, the time serialization startsignal 416 indicated in FIG. 4 is delivered.

FIG. 9 is a diagram showing the learning method of a neural networkwhich is used for the estimation of the vehicle weight. Referring to thefigure, vehicle weight estimation means 901 is constructed of theRumelhart type neural network which consists of an input layer, anintermediate layer and an output layer. Each of the three layersincludes one or more neurons or arithmetic elements, and the neurons ofthe adjacent layers are coupled by synapses. Signals are transmittedalong the input layer → the intermediate layer → the output layer. Eachof the synapses is endowed with a weight, and the output signal of thecorresponding neuron is multiplied by the weight of the synapse to formthe input signal of the next neuron. Each neuron converts the sum of theinput signals into the output signal by the use of a sigmoidal function.

The neural network 901 learns the vehicle weight in such a way that theweights of the respective synapses are so altered as to diminish theerror between the true weight of the automobile and the vehicle weightestimated from the inputs of the acceleration, vehicle speed andthrottle valve opening. In order to cope with various aspects ofdepressing the accelerator pedal, accelerating response waveforms arepreviously measured by experiments based on the time serializationmethod shown in FIG. 4, while the vehicle weight and the throttle valveopening are being changed on an identical automobile. Subsequently, thetime-serial waveforms of the acceleration, vehicle speed and throttlevalve opening are input to the neural network 901, thereby obtaining theestimated vehicle weight 911. Next, the error 913 of the estimatedvehicle weight 911 with respect to the true vehicle weight 912 iscalculated.

Weight alteration means 902 alters the weights of the inter-layersynapses so as to diminish the error 913 between the estimated vehicleweight 911 and the true vehicle weight 912. As an algorithm for alteringthe weights, a back-propagation algorithm is typical, but anotheralgorithm may well be employed.

A running load is estimated in order to perform the shift control inaccordance therewith. Herein, the running load is evaluated byestimating an output torque and solving the equation of motion on thebasis of the estimated output torque, the acceleration and the estimatedvehicle weight.

Regarding the output torque estimation, there is a method in which theoutput torque is estimated from the slip and r.p.m. (also termed“revolution number” or “speed”) of the torque converter in accordancewith torque converter characteristics, and a method in which it isestimated from the r.p.m. of the engine and the opening of the throttlevalve in accordance with engine torque characteristics.

The estimation method based on the slip of the torque converter canestimate the output torque precisely when the slip of the torqueconverter is great, that is, when the ratio between the revolutions ofthe input and output of the torque converter is small. This method,however, exhibits an inferior precision in a region where the slip issmall, that is, where the ratio between the input revolutions and theoutput revolutions is great.

On the other hand, the estimation method based on the engine torquecharacteristics exhibits a constant precision in the whole operatingregion of the engine, but it has the problem that torques required foroperating accessories such as an air conditioner cannot be found.

In this embodiment, accordingly, in the region where the slip of thetorque converter is great, the output torque is estimated on the basisof the torque converter, while at the same time, the torques necessaryfor operating the accessories such as the air conditioner are estimated.Besides, in the region where the slip of the torque converter is small,the output torque is calculated in such a way that the torques for theaccessories estimated before are subtracted from the estimated torquebased on the engine.

FIG. 10 is a diagram for explaining the method of estimating the outputtorque and the method of estimating the load. In estimating the outputtorque from a torque generated by the engine, an engine output torque1015 (Te) is derived from an engine torque map (engine-generated torqueestimation means) 1001 on the basis of a throttle valve opening 1011(TVO) and an engine revolution speed (or r.p.m.) 1012 (Ne). The totalload torque 1016 (Tacc) of the accessories such as the air conditioneris subtracted from the engine output torque 1015, and the resultingdifference is multiplied by the torque ratio 1017 (t) of the torqueconverter, thereby obtaining a turbine torque 1014 (Tt1) based on theengine revolution speed 1012.

On the other hand, in estimating the output torque from the pumprevolution speed or r.p.m. (namely, the engine revolution speed) 1012and turbine revolution speed or r.p.m. 1013 (Nt) of the torqueconverter, the ratio Nt/Ne between the turbine revolution speed 1013 andthe engine revolution speed 1012 is calculated, and the torque ratio1017 and pump torque capacity coefficient 1018 (τ) of the torqueconverter are derived from a torque converter-torque characteristic map1002. The pump torque capacity coefficient 1018 of the torque converteris multiplied by the square of the engine revolution speed 1012, therebyobtaining a pump torque. Further, the pump torque is multiplied by thetorque ratio 1017. Then, a turbine torque 1019 is obtained.

Accessory torque estimation means 1003 compares the estimated turbinetorque 1014 based on the engine and the estimated turbine torque 1019based on the torque converter. Herein, when the ratio Nt/Ne between theturbine revolution speed and the engine revolution speed is smaller than0.8, the estimated accessory torque 1016 is output so as to nullify theerror between the turbine output torque 1014 based on the engine and theturbine output torque 1019 based on the torque converter. In contrast,when the ratio Nt/Ne between the turbine revolution speed and the enginerevolution speed is not smaller than 0.8, the latest estimated accessorytorque 1016 is output.

Here in this example, the output of the accessory torque estimationmeans 1003 is changed-over at Nt/Ne =0.8. However, the value 0.8 differsdepending upon the characteristics of torque converters, and a valuenear the clutch point of the pertinent torque converter may be set. Thereason is that the Nt/Ne values corresponding to the large errors of thepump torque capacity coefficient of the torque converter are bounded bythe clutch point.

Turbine torque estimation means 1004 delivers the turbine torque basedon the torque converter, as an estimated turbine torque when the ratioNt/Ne (1021) between the turbine revolution speed and engine revolutionspeed of the torque converter is smaller than 0.8, and it delivers theturbine torque based on the engine, as an estimated turbine torque whennot. The estimated turbine torque 1022 (Tt) thus produced is multipliedby a gear ratio 1024 (r), thereby obtaining an estimated output torque1023 (To). An estimated running load torque 1028 (TL) is calculated insuch a way that the product 1025 (M × rw) between the estimated vehicleweight 126 (refer also to FIG. 1) and the effective radius rw of a typeor wheel is multiplied by a longitudinal acceleration 1026 (α),whereupon the resulting product 1027 is subtracted from the estimatedoutput torque 1023.

FIGS. 11(a) and 11(b) illustrate an engine torque map and a torqueconverter characteristic map, respectively. The engine torque map inFIG. 11(a) indicates the generated torque Te with the throttle valveopening set as a parameter, by taking the revolution speed Ne of theengine on the axis of abscissas. On the other hand, the torque convertercharacteristic map in FIG. 11(b) indicates the pump torque capacitycoefficient σ and the ratio t of the input and output torques of thetorque converter, by taking the ratio e of the input and outputrevolutions of the torque converter on the axis of abscissas.

FIG. 12 illustrates the flow of the processing of the accessory torqueestimation means 1003 shown in FIG. 10. More specifically, the accessorytorque is set at Tacc =0 at a step 1201. If the slip e of the torqueconverter, namely, the aforementioned ratio Nt/Ne between the turbinerevolution speed 1013 and the engine revolution speed 1012 is smallerthan 0.8, is checked at a step 1202. When the slip e is smaller than0.8, the processing flow proceeds to a step 1203, and when not, itreturns to the step 1202. At the step 1203, the difference Terr betweenthe estimated turbine torque Tt1 based on the engine and the estimatedturbine torque Tt2 based on the torque converter is evaluated as Terr =Tt1 − Tt2. At the next step 1204, the estimated accessory torque Tacc iscalculated as Tacc = Tacc + Terr/t where t denotes the torque ratio ofthe torque converter.

FIG. 13 illustrates the flow of a process for obtaining the estimatedturbine torque Tt1 based on the engine. At a step 1301, the values ofthe engine revolution speed Ne and the throttle valve opening TVO areread. At the next step 1302, the engine torque Te is derived from theengine torque map 1001 in FIG. 10 (refer also to FIG. 11(a)) on thebasis of the engine revolution speed Ne and the throttle valve openingTVO. At the subsequent step 1303, the turbine torque Tt1 based on theengine is calculated in such a way that the accessory torque Tacc issubtracted from the engine torque Te, whereupon the resulting differenceis multiplied by the torque ratio t of the torque converter.

FIG. 14 illustrates the flow of a process for obtaining the estimatedturbine torque Tt2 based on the revolutions of the torque converter. Ata step 1401, the values of the vehicle speed Vsp, engine revolutionspeed Ne and gear ratio r are read. Subsequently, the turbine revolutionspeed Nt is computed from the vehicle speed Vsp and the effective radiusrw of the wheel at a step 1403. At the next step 1405, the slip e of thetorque converter is calculated, and the pump torque capacity coefficientσ and the torque ratio t of the torque converter are derived from thetorque converter characteristic map 1002 in FIG. 10 (refer also to FIG.11(b)). At the subsequent step 1406, the turbine torque Tt2 (1019 inFIG. 10) based on the torque converter is calculated in such a way thatthe square of the engine revolution speed Ne is multiplied by the pumptorque capacity coefficient σ, thereby obtaining the pump torque Tp,whereupon the pump torque Tp is multiplied by the torque ratio t of thetorque converter.

Incidentally, in this process, the turbine revolution number Nt may wellbe directly obtained instead of being computed from the vehicle speedVsp. In such as case, the steps 1401 and 1403 are respectively replacedwith steps 1402 and 1404. More specifically, the value of the enginerevolution speed Ne is read at the step 1402, and the value of theturbine revolution speed Nt is read at the step 1404.

FIG. 15 illustrates the flow of a process for obtaining the estimatedload torque TL from the estimated output torque To and the accelerationα. Whether the revolution ratio e of the torque converter is smallerthan 0.8 is checked at a step 1501. When the ratio e is smaller, theflow proceeds to a step 1502, and when not, it proceeds to a step 1503.At the step 1502, the estimated turbine torque Tt is set at the turbinetorque Tt2 based on the torque converter, whereupon the flow proceeds toa step 1504. On the other hand, at the step 1503, the estimated turbinetorque Tt is set at the turbine torque Tt1 based on the engine,whereupon the flow proceeds to the step 1504. Subsequently, at the step1504, the estimated turbine torque Tt is multiplied by the gear ratio r,thereby obtaining the estimated output torque To. At the next step 1505,the estimated load torque TL is calculated in such a way that theproduct among the estimated vehicle weight M, the effective radius rw ofthe wheel and the acceleration α is subtracted from the estimated loadtorque TL.

FIG. 16 illustrates another method of evaluating torques required forthe accessories. This method consists in that the torques of theaccessories are set for the individual devices beforehand, and that,when the pertinent device is “ON”, the corresponding value is added. Inthe figure, the torque of an air conditioner is taken as an example.

At a step 1601, Tacc = 0 is set. If the air conditioner is “ON”, ischecked at a step 1602. When the air conditioner is “ON”, the flow ofthe method proceeds to a step 1603, and when not, the processing of themethod is ended. At the step 1603, the accessory torque Tacc is set atTacc = Tacc + Tac where Tac denotes the torque of the air conditioner.

There will now be explained a control in which a shift pattern ischanged on the basis of an estimated load and an estimated vehicleweight. FIG. 17 is a block diagram of gear position determination meansfor determining a gear position from the estimated vehicle weight andthe estimated load.

An upshifting speed change line selector 1701 receives a vehicle weightsignal 1711 and a load signal 1712 as inputs, and it delivers anupshifting speed change line 1714 to gear position final-determinationmeans 1703 as an output. A downshifting speed change line selector 1702receives the load signal 1712 as an input, and it delivers adownshifting speed change line 1715 as an output. The gear positionfinal-determination means 1703 receives a vehicle speed signal 1716 anda throttle valve opening signal 1717 in addition to the upshifting speedchange line 1714 and the downshifting speed change line 1715, and itdelivers a gear shift signal 1713.

FIGS. 18(a) and 18(b) illustrate the controls based on the vehicleweight and the load, for upshift and for downshift, respectively. Ashift map as shown in FIG. 18(a) is used for the upshift, while a shiftmap as shown in FIG. 18(b) is used for the downshift.

In the case of the upshift, the gear shift boundary follows betweenlines {circle around (1)}, {circle around (2)} or {circle around (3)}dependent on the vehicle weight and the load moving from line 1 → 2 → 3as such weight and speed increase. On the other hand, in the case of thedownshift, the speed change line moves between lines {circle around(A)}, {circle around (B)} and {circle around (C)} as the local enlarges.

In the case of the downshift, when the throttle valve opening (θ + h) issmall, the speed change line {circle around (A)} moves toward the highervehicle speed Vsp. This is intended to apply engine braking.

Although the gear shift boundary is determined from the vehicle weightand the running load in the above embodiment, it may well be determinedfrom only the running load.

In addition, although any of the preset gear shift boundaries isselected in the above embodiment, the gear shift boundary may well becontinuously varied on the basis of the estimated load, the vehicleweight and a grade or slope. A method for the continuous variation maybe such that two gear shift boundaries which do not intersect each otherare set, and that they are divided internally or externally in thedirection of, for example, the vehicle speed. This method will beexplained in detail below.

FIG. 19 is a block diagram showing another embodiment of the automatictransmission control system for an automobile in which the gear shiftboundary is determined from the gradient (an inclination angle) and thevehicle weight.

This system comprises a gradient resistance (hill-climbing resistance)calculation unit (load estimation means) 1901, a continuously variablequantity calculation unit 1902, a continuous variation unit 1903, ashift pattern-A memory 1904 and a shift pattern-B memory 1905. Thecontinuously variable quantity calculation unit 1902 and the continuousvariation unit 1903 constitute a shift schedule variable-control unit.The shift pattern-A memory 1904 and the shift pattern-B memory 1905constitute means for storing shift schedules therein.

The gradient resistance calculation unit (load estimation means) 1901 issupplied with the gradient θ and the vehicle weight W, and it calculatesa gradient increment resistance ΔL in accordance with the followingequation (1):ΔL=W·g·sin θ  (1)where g denotes the gravitational acceleration.

The continuously variable quantity calculation unit 1902 calculates acontinuously variable quantity Z in accordance with the followingequations (2) and (3): $\begin{matrix}{{y = \frac{\Delta\quad L}{{Wm} \cdot s}}( {{vy} = {\frac{W}{Wat} \cdot 0}} )} & (2)\end{matrix}$where y denotes a gradient equivalent coefficient, which may well becalculated by the aforementioned equation $y = {\frac{W}{Wat} \cdot 0.}$Besides, Wst represents a standard vehicle weight previously set as adefault, and ε represents a continuously variable quantity-conversioncoefficient.

The continuous variation unit 1903 determines a gear position in such away that a value X indicated by Equation (4) below is calculated fromthe continuously variable quantity Z, whereupon the gear shift boundaryis variably obtained on the basis of the value X and the throttle valveopening as illustrated in FIG. 20. Shift patterns A and B indicated inFIG. 20 are respectively sent from the shift pattern-A memory 1904 andthe shift pattern-B memory 1905. Thus, a smooth shift operationconforming to the gradient is realized.X = X1 + (X2 − X1)·Z  (4)

There will now be explained a case where a gear position is determinedfrom the vehicle weight, the gradient and an acceleration request. Inthis case, the gradient increment resistance in FIG. 19 is evaluated asstated below. Processing after the evaluation of the gradient incrementresistance is the same as in FIG. 19. First, the temporal variation ofthe throttle valve opening as shown in FIG. 21(a) is measured.Subsequently, the time derivative of the throttle valve opening isobtained as shown in FIG. 21(b). The acceleration request α iscalculated in accordance with the preset functional relationship of thefollowing equation (5), on the basis of the throttle valve opening (TVO)and the time derivative thereof:α=f(ΔTVO/ΔT, TVO, t)  (5)

An example of the obtained result of the acceleration request α is shownin FIG. 21(c). In this manner, the presence of the acceleration requestα is decided when the throttle valve opening and the differentiatedvalue thereof have predetermined values or above.

The gradient increment resistance ΔL is calculated by the followingequation (6) on the basis of the vehicle weight W, the gradient θ andthe decided acceleration request α:ΔL = W·g·sin θ + W·α  (6)

With this embodiment, a smooth shift operation with the accelerationrequest also taken into consideration can be realized.

As described above, according to the present invention, the vehicleweight is estimated from the drive characteristics of the automobile,the output torque is estimated from the slip of the torque converter orfrom the revolution speed of the engine and the opening of the throttlevalve, and the running load is estimated from the output torque and theacceleration. Then, in the upshift operation, the gear shift boundary ismoved by utilizing both the vehicle weight and the running load, whilein the downshift operation, it is moved in consideration of only therunning load. Thus, the fuel consumption is enhanced, and the exactshift operation conformed to the drive conditions is realized.

Incidentally, although the foregoing embodiments have been described asestimating the vehicle weight, the present invention is not restrictedthereto. The vehicle weight may well be directly measured by a sensor.

According to the present invention, a running load is estimated, and ashift operation conformed to a vehicle weight and the running load isperformed. It is therefore possible to provide an automatic transmissioncontrol system for an automobile in which the optimal shift pattern isformed in conformity with a driving environment (such as driving on amountain path, or driving with many passengers on board), therebyenhancing the drivability of the automobile, and in which the fuelconsumption of the automobile is enhanced more than in the prior artwhen driving on a flat road.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

1. System for controlling selection of gear position for an automatictransmission of an automobile comprising: weight estimation means forestimating a total weight of said automobile; acceleration input meansfor receiving an acceleration signal indicative of acceleration of saidautomobile; output torque estimation means for estimating an outputtorque based on torque characteristics of a drive train of saidautomobile; running load estimation means for estimating a running loadfrom the estimated weight of the automobile, the acceleration, and theestimated output torque; memory means for storing at least two shiftschedules therein; a shift schedule variable-control unit whichdetermines a shift schedule of an automatic transmission of said drivetrain during actual running of said automobile on the basis of theestimated running load, the estimated weight of the automobile and thestored shift schedules; and gear shift determination means for selectinga gear position of said automatic transmission based on thedetermination shift schedule; wherein said output torque estimationmeans estimates said output torque based on torque characteristics of anengine of said drive train when a ratio between an input revolutionspeed and an output revolution speed of said torque converter is greaterthan a predetermined value, and based on torque characteristics of atorque converter of said automatic transmission when said ratio is lessthan said predetermined value.
 2. System for controlling selection ofgear position for an automatic transmission of an automobile,comprising: weight estimation means for estimating a total weight ofsaid automobile; acceleration input means for receiving an accelerationsignal indicative of acceleration of said automobile; output torqueestimation means for estimating an output torque based on torquecharacteristics of a drive train of said automobile; running loadestimation means for estimating a running load from the estimated weightof the automobile, the acceleration, and the estimated output torque;memory means for storing at least two shift schedules therein; a shiftschedule variable-control unit which determines a shift schedule of anautomatic transmission of said drive train during actual running of saidautomobile on the basis of the estimated running load, the estimatedweight of the automobile and the stored shift schedules; gear shiftdetermination means for selecting a gear position of said automatictransmission based on the determined shift schedule; and a neuralnetwork which has stored therein values of at least a throttle valveopening and said acceleration of the automobile for learning values of avehicle weight corresponding to the values of at least said throttlevalve opening and said accelerations; wherein said vehicle weightestimation means estimates said vehicle weight by time-serializing eachof at least said throttle valve opening and said acceleration and thensupplying resultant time-serial signals to said neural network.
 3. Anautomatic transmission control system for an automobile as defined inclaim 2, wherein said vehicle weight estimation means includes means forsupplying said time-serial signals of said throttle valve opening andsaid acceleration, commencing when said throttle valve opening hasexceeded a second predetermined value and said acceleration has alsoexceeded a third predetermined value.
 4. System for controllingselection of gear position for an automatic transmission of anautomobile, comprising: weight estimation means for estimating a totalweight of said automobile; acceleration input means for receiving anacceleration signal indicative of acceleration of said automobile;output torque estimation means for estimating an output torque based ontorque characteristics of a drive train of said automobile; running loadestimation means for estimating a running load from the estimated weightof the automobile, the acceleration, and the estimated output torque;memory means for storing at least two shift schedules therein; a shiftschedule variable-control unit which determines a shift schedule of anautomatic transmission of said drive train during actual running of saidautomobile on the basis of the estimated running load, the estimatedweight of the automobile and the stored shift schedules; and gear shiftdetermination means for selecting a gear position of said automatictransmission based on the determined shift schedule; wherein saidvehicle weight estimation means estimates said vehicle weight of saidautomobile in response to a throttle valve opening signal and a vehiclespeed signal in addition to said acceleration signal; and wherein saidoutput torque estimation means estimates said output torque in responseto a revolution speed signal of an engine of said drive train and aturbine revolution speed signal of a torque converter of said automatictransmission.
 5. System for controlling selection of gear position foran automatic transmission of an automobile, comprising: weightestimation means for estimating a total weight of said automobile;acceleration input means for receiving an acceleration signal indicativeof acceleration of said automobile; output torque estimation means forestimating an output torque based on torque characteristics of a drivetrain of said automobile; running load estimation means for estimating arunning load from the estimated weight of the automobile, theacceleration, and the estimated output torque; memory means for storingat least two shift schedules therein; a shift schedule variable-controlunit which determines a shift schedule of an automatic transmission ofsaid drive train during actual running of said automobile on the basisof the estimated running load, the estimated weight of the automobileand the stored shift schedules; and gear shift determination means forselecting a gear position of said automatic transmission based on thedetermined shift schedule; wherein said output torque estimation meanshas a first mode in which said output torque is estimated from a turbinerevolution speed of a torque converter of said automatic transmissionand a revolution speed of an engine of said drive train, and a secondmode in which said output torque is estimated from a throttle valveopening of said engine and said revolution speed of said engine, one ofsaid first and second modes being selected in response to a ratiobetween an input and an output revolution speeds of said torqueconverter of said automatic transmission.
 6. Method of controllingselection of gear position for automatic transmission of an automobilehaving means for storing a plurality of shift schedules for saidautomatic transmission, said method comprising the steps of: first,calculating an estimated weight of said automobile; second, determiningacceleration of said automobile; third, calculating a value for anoutput torque of said transmission based on torque characteristics of adrive train of said automobile and generating an output torque signalindicative of said output torque value; fourth, estimating a runningload of said automobile based on said estimated weight of saidautomobile, the acceleration, and the output torque signal; fifth,selecting a shift schedule from among a plurality of shift schedulesstored in said means for storing, based on the estimated running loadand the estimated weight of the automobile; and sixth, selecting a gearposition of said automatic transmission based on the selected shiftschedule; wherein said third step comprises calculating said outputtorque based on torque characteristics of an engine of said drive trainwhen a ratio between an input revolution speed and an output revolutionspeed of a torque converter of said automatic transmission is greaterthan a predetermined value, and calculating said output torque based ontorque characteristics of said torque converter of said automatictransmission when said ratio is less than said predetermined value. 7.Method of controlling selection of gear position for automatictransmission of an automobile having means for storing a plurality ofshift schedules for said automatic transmission, said method comprisingthe steps of: first, calculating an estimated weight of said automobile;second, determining acceleration of said automobile; third, calculatinga value for an output torque of said transmission based on torquecharacteristics of a drive train of said automobile and generating anoutput torque signal indicative of said output torque value; fourth,estimating a running load of said automobile based on said estimatedweight of said automobile, the acceleration, and the output torquesignal; fifth, selecting a shift schedule from among a plurality ofshift schedules stored in said means for storing, based on the estimatedrunning load and the estimated weight of the automobile; and sixth,selecting a gear position of said automatic transmission based on theselected shift schedule; wherein said third step comprises calculatingsaid output torque based on at least torque characteristics of a torqueconverter of said automatic transmission, and torque characteristics ofan engine of said drive train; and wherein said third step comprisescalculating said output torque based on said torque characteristics ofthe engine of said drive train when a ratio between an input revolutionspeed and an output revolution speed of said torque converter of saidautomatic transmission is greater than a predetermined value, andcalculating said output torque based on said torque characteristics ofsaid torque converter of said automatic transmission when said ratio isless than said predetermined value.
 8. Control system for an automatictransmission with torque converter comprising: first input torqueestimating unit for estimating an input-torque of said automatictransmission using an engine torque characteristic; second input torqueestimating unit for estimating an input-torque of said automatictransmission using torque-converter characteristic; selecting unit forcomparing the ratio between turbine revolution speed and enginerevolution speed (Nt/Ne) and a threshold value, selecting an estimatedvalue from among estimated values from the first input-torque estimatingunit and the second input-torque estimating unit in accordance with thecomparison result, and outputting the estimated value selected as anestimated torque value, and control unit for controlling the automatictransmission using the estimated torque value outputted from theselecting unit.
 9. Control system for an automatic transmission withtorque converter comprising: first input torque estimating unit forestimated an input-torque of said automatic transmission using an enginetorque characteristic; second input torque estimating unit forestimating an input-torque of said automatic transmission usingtorque-converter characteristic; selecting unit for comparing the ratiobetween turbine revolution speed and engine revolution speed (Nt/Ne) anda threshold value, selecting an estimated value from the firstinput-torque estimating unit when an ratio (Nt/Ne) is not smaller thanthe threshold and selecting an estimated value from the secondinput-torque estimating unit when the ration (Nt/Ne) is less than thethreshold, and outputting the estimated value selected as an estimatedtorque value; and control unit for controlling the automatictransmission using the estimated torque value from the selecting unit.10. Control system for an automatic transmission with torque convertercomprising: first input torque estimating unit for estimating aninput-torque of said automatic transmission using an engine torquecharacteristic; second input torque estimating unit for estimating aninput-torque of said automatic transmission using an engine torquecharacteristic; storing unit for comparing the ratio between turbinerevolution speed and engine revolution speed (Nt/Ne) and a thresholdvalue, and memorizing a deviation of estimated values from the firstinput-torque estimating unit and the second input-torque estimating unitwhen the ratio (Nt/Ne) is less than the threshold; calculation unit forcomparing the ratio between turbine revolution speed and enginerevolution speed (Nt/Ne) and a threshold value, and calculating anestimated torque value by correcting an estimated value from the firstinput-torque estimating unit using the memorized deviation when theratio (Nt/Ne) is not smaller than the threshold; and control unit forcontrolling the automatic transmission using the estimated torque valuefrom the calculating unit.